Speaking to reporters in Hong Kong on Thursday following his release on bail, Mr Lam said he was arrested after crossing the border from Hong Kong into the southern mainland Chinese city of Shenzhen in October.

“I was covered up the whole time. They blindfolded me and put a cap on my head, and basically bundled me up,” Mr Lam said.

He said his captors put him on a train for 13 to 14 hours that took him to the eastern Chinese city of Ningbo, where he was initially detained.

“I couldn’t believe this could happen to me. It was very surreal. I thought I was in another world and even hoped my situation was a dream and not reality,” he said.

“As a Hongkonger, I am a free man.”

A demonstrator wears a Lee Bo maskCredit:
Reuters

Mr Lam also refuted recent claims by Lee Bo, one of his four colleagues at the Mighty Current publishers, that the British passport holder had left Hong Kong voluntarily in December to assist with an investigation.

Mr Lee had told him that he had been “taken away from Hong Kong”, Mr Lam said.

Four of the booksellers have returned from the mainland after being released on bail. But three of them soon travelled back over the border, apparently of their own volition. A fifth remains in detention.

Mr Lam said his release on bail, on Tuesday, was on the condition that he also returned to the Chinese mainland, in his case with details of 600 customers who purchased books from Mighty Current’s Causeway Bay store.

Lam Wing-kee Credit:
AP

He said he had spent two sleepless nights making the decision to speak out.

"If I don't speak up Hong Kong will be hopeless. It's not just a personal matter," he said. "I dare not go back."

The 61-year-old also spoke about his appearance in a “confession” that was broadcast on Chinese television in February which featured the other four men.

“There was a director and there was script,” Mr Lam said, according to the Hong Kong-based South China Morning Post.

“I had to memorise the lines and read them in front of TV. If I could not recount the lines, there would be a re-take,” he added.

Mr Lam also said he had no choice but to agree to do the TV confession. "I was in fear. I felt helpless. I didn't know what they would do to me."

Asked about Lee Bo’s claim after he was released in March that he had entered and left the mainland voluntarily, Mr Lam said: “Obviously, it was exactly the same situation in which I was forced to make a televised confession.”

The case of Mr Lee caused the greatest concern among observers as he was the only one to go missing from Hong Kong. His disappearance raised concerns that mainland law enforcement agents were operating illegally in the city.

Hong Kong was returned to China by Britain in 1997 and supposedly enjoys far greater liberties than the mainland.